In this paper, we extend the previous work by performing the first simultaneous and overconstrained fit of unpolarized PDFs and FFs that utilizes both charged hadron production in semi-inclusive deep-inelastic scattering (SIDIS) and single-inclusive \(e^+ e^-\)  annihilation (SIA).
This is partly motivated by a number of recent observations associated with the study of TMD PDFs.
For example, significant tension has recently been found between fits performed with standard sets of PDFs and FFs and fixed order perturbative QCD calculations in processes including SIDIS [1]}, [2]}, Drell-Yan (DY) [3]}, and SIA into wide-angle hadron pairs [4]}.
A number of suggested solutions and explanations have been proposed to account for this, including a possible need for power suppressed corrections [5]} at the moderate scales of most SIDIS experiments.
However, more tests of the limits of applicability of standard collinear factorization are needed before it is possible to draw firm conclusions.
Given that the majority of data used to constrain collinear correlation functions (both PDFs and FFs) are either highly inclusive or exist are at very high scales, or both, it is perhaps not surprising that tension arises when these are evolved downward and used to make predictions at lower scales and for highly differential observables.
Indeed, there have been few tests that \(Q^2\) -scaling, a hallmark of the collinear perturbative regime, actually holds to a reasonable approximation in SIDIS measurements at moderate \(Q^2\) .
Our hope is that the new combined fit, which we refer to as “JAM20-SIDIS”, will help to shed light on this and similar issues in the future.
